#include<iostream>
using namespace std;
typedef long long LL;
const int N = 60;
int f[N][N];
int n, m, t;
int main()
{
	cin >> n >> m >> t;
	int k = n + m;
	for (int i = 0; i < N; i++) {
		for (int j = 0; j <= i; j++) {
			if (!j)f[i][j] = 1;
			else {
				f[i][j] = f[i - 1][j - 1] + f[i - 1][j];
			}
		}
	}
	LL sum = 0;
	for (int i = 1; i <= t; i++) {
		if(i>=1&&t-i>=4){
			sum = sum + f[m][i] * f[n][t - i];
		}
	}
	cout << sum << endl;
	return 0;
}